/*
 * OREKIT-X
 * Copyright 2002-2008 CS Communication & Systemes
 * 
 * Parts of this software package have been licensed to CS
 * Communication & Systemes (CS) under one or more contributor license
 * agreements.  See the NOTICE file distributed with this work for
 * additional information.
 *  
 * This is an experimental copy of OREKIT from www.orekit.org.
 * Please use the original OREKIT from orekit.org for normal work
 * unrelated to this research project.
 * 
 * Licensed under the Apache License, Version 2.0 (the "License"); you
 * may not use this file except in compliance with the License.  You
 * may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
 * implied.  See the License for the specific language governing
 * permissions and limitations under the License.
 */
package ore.propagation.events;

import ore.SpacecraftState;
import ore.errors.OrekitException;
import ore.time.AbsoluteDate;

/** 
 * A function related to date events.Theeentourred
 * 
 * This class finds date events (i.e. occurrence of a predefined date).
 * 
 * The default implementation behavior is to {@link EventDetector#STOP
 * stop} propagation at date occurrence. This can be changed by overriding the
 * {@link #eventOccurred(SpacecraftState, boolean) eventOccurred} method in a
 * derived class.
 * 
 * @see ore.propagation.Propagator#addEventDetector(EventDetector)
 * @see ore.forces.maneuvers.ConstantThrustManeuver
 * 
 * @author Luc Maisonobe
 */
public class DateDetector
    extends AbstractDetector
{

    public final AbsoluteDate target;


    public DateDetector(final AbsoluteDate target) {
        super(1.0e9, 1.0e-10);
        this.target = target;
    }


    /**
     * Handle a date event and choose what to do next.
     * 
     * The default implementation behavior is to {@link
     * EventDetector#STOP stop} propagation at date occurrence.  This
     * can be changed by overriding the {@link
     * #eventOccurred(SpacecraftState, boolean) eventOccurred} method
     * in a derived class.
     * 
     * @param s The current state information : date, kinematics, attitude
     * 
     * @param increasing If true, the value of the switching function increases
     * when times increases around event (note that increase is measured with respect
     * to physical time, not with respect to propagation which may go backward in time)
     * 
     * @return One of {@link #STOP}, {@link #RESET_STATE}, {@link #RESET_DERIVATIVES}
     * or {@link #CONTINUE}
     * 
     * @exception OrekitException if some specific error occurs
     */
    public int eventOccurred(SpacecraftState s, boolean increasing)
        throws OrekitException
    {
        return STOP;
    }
    /** {@inheritDoc}
     */
    public double g(SpacecraftState s) throws OrekitException {
        return s.getDate().durationFrom(target);
    }
}
